Service Center

Plexi Palace services all manner of vacuum tube guitar amplifiers and related products. We specialize in rare and high value pieces to who you would not trust to just anyone.

Craig at the bench
Craig Tathwell has teched with the Plexi Palace for 18 years. He has 36 years of electronics experience. He is an expert in tube hifi, guitar amps and high end audio products.

The Plexi Palace has been rebuilding and selling Old vintage Marshall, Vox, Hiwatt, Selmer, Orange and Watkins amps since 1997. We have been building Mojaveamps since 2001. We also service a large number of other tube guitar amplifiers especially old Fenders. Each amplifier that comes into our shop goes through a thorough servicing and inspection process.

This is one of two power supplies we use to “Re-Form” the electrolytic capacitors inside precious vintage amplifiers. This power supply is able to produce 500VDC. It is connected directly to the capacitors and while being monitored for leakage current, the capacitor is slowly ramped up to its full voltage. This process can take a ½ hour or several hours depending on the condition of the old capacitors. This is a vital process in restoring the amplifier.

Each Amp is inspected mechanically and electrically. Great care is taken to inspect each solder joint and each part to identify if it has been replaced. If so we make sure it is a correct type and value. If possible we use our Old Stock Original parts if the situation calls for it. Otherwise we correct any problems with a properly fit new part that is needed.

Each amp”s output transformer is identified. We measure the transformers primary input impedance which tells us if the amp was originally equipped with KT66 or EL34 power tubes. All tubes are tested and run on the Amplitrex AT-1000 and on the amplifier being serviced. Each amp has its bias set for optimal operation. Factory settings are used to make sure each amp sounds as it did when it was built.

During the biasing process of  vintage Marshall amps, we try hard to use the original Marshall design of a single bias resistor, typically 56K rather then an adjustable pot. This may be difficult since tubes change over the years. Tubes that are replaced might run hot or cold. We work through our inventory of original Marshall resistors first to find the correct value. If replacement is required we use a period correct resistor since Marshall used several different resistor styles in its first few years of production.

While the biasing process takes place we monitor AC Heater Voltage, AC Line Voltage, Power Tube Plate Current and High Tension Voltage (Also known as B+). Each amplifier’s correct operating line voltage is identified for the user. This might be 100, 105, 110, 115 or 240 VAC. In addition, the biasing will set up the amplifiers high voltage to be under the maximum limit of the internal electrolytic filter capacitors. That protects and preserves the original parts for many years of trouble free use. In addition we make sure that the idle current on the power tubes is optimized for excellent sound quality.

A lengthy burn in process is done to insure the finished product will perform without trouble. This is also where the waveform is analyzed for any irregularities, oscillations or excessive crossover distortion. Once a burn in process is completed each amplifier is tested with a guitar and speaker. With the final test the amplifier is given a clean bill of health.

We are experts in Hiwatt, Vox, Orange, Fender, Marshall, Selmer and most all early British and American vintage tube and solid state amplifiers.

Safe, quick and reliable service. The customer comes first always.

Victor with some of the Marshalls that we had at the shop.

Mojave Ampworks and Plexi Palace Mascot
Our Mascot

Victor with some of the Hiwatts that we had at the shop

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